1. Technical Field
The present invention relates to an image processing device that drives an image sensor to acquire an image of a medium when exposed to visible light and an image of the medium exposed to ultraviolet light, and to an image processing method and a program.
2. Related Art
When a check is presented to a financial institution, the check is read by a check processing device, magnetic ink characters printed on the check are magnetically read, and payment is processed based on the acquired magnetic information. Parallel to reading the magnetic ink characters, the check processing device also emits visible light to the front of the check to capture an image of the check, and the financial institution stores the acquired check image as proof of the transaction. When a check bearing a security image printed with UV ink that fluoresces when exposed to ultraviolet light to prevent forgery is presented to a financial institution, the check processing device reads the front of the check with UV light by exposing it to UV light, and the acquired check image is used to determine the authenticity of the check. The financial institution also saves the check image captured using ultraviolet light as proof of the transaction.
One example of a check processing device that can be used in such check payment processes is described in JP-A-2013-70225. The check processing device described in JP-A-2013-70225 has a magnetic sensor for magnetically reading magnetic ink characters, and an image sensor for exposing the surface of the check to light and optically imaging the check. The image sensor images the check using both visible light and ultraviolet light.
A problem with storing an image of the check exposed to visible light and an image of the check exposed to ultraviolet light as proof of payment by a check is that the amount of image data to be stored increases. To reduce the amount of image data stored as proof of a transaction, the image of the check when exposed to visible light and the image of the check when exposed to ultraviolet light could conceivably be combined to store a single synthesized image.
However, in an image that is captured by the image sensor reading the surface of the check when exposed to ultraviolet light, the portions that capture the reflection of ultraviolet light reflected from the surface of the check are dark, and the portions that image the fluorescence of the portions printed with UV ink are light gray scale images. Furthermore, because the area of the portion printed with UV ink is small compared with the total area of the check, the check image is dark overall. Therefore, when the image of the check exposed to visible light and the image of the check exposed to ultraviolet light are combined, contrast drops in the synthesized image and the security image becomes hard to recognize.